Wireless communication method and wireless communication device for broadband link configuration

ABSTRACT

The present invention relates to a wireless communication method and a wireless communication terminal for wideband link setup, and more particularly, a wireless communication method and a wireless communication terminal for increasing data communication efficiency by extending a data transmission bandwidth of a terminal. 
     To this end, provided are a wireless communication method of a terminal, including: obtaining first primary channel information of a basic service set (BSS) with which the terminal is associated; performing clear channel assessment (CCA) for one or more secondary channels of the BSS; and setting a second primary channel among one or more secondary channels determined to be idle based on a result of the CCA, and a wireless communication terminal using the same.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal for wideband link setup, and moreparticularly, to a wireless communication method and a wirelesscommunication terminal for increasing data communication efficiency byextending a data transmission bandwidth of a terminal.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using frequencies of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using frequencies of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses frequencies of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequencies of the 2.4 GHz band which aresignificantly congested and improves the communication speed up to amaximum of 54 Mbps by using an OFDM technology. However, the IEEE802.11a has a disadvantage in that a communication distance is shorterthan the IEEE 802.11b. In addition, IEEE 802.11g uses the frequencies ofthe 2.4 GHz band similarly to the IEEE 802.11b to implement thecommunication speed of a maximum of 54 Mbps and satisfies backwardcompatibility to significantly come into the spotlight and further, issuperior to the IEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of a radiointerface accepted by 802.11n, such as a wider radio frequency bandwidth(a maximum of 160 MHz), more MIMO spatial streams (a maximum of 8),multi-user MIMO, and high-density modulation (a maximum of 256 QAM).Further, as a scheme that transmits data by using a 60 GHz band insteadof the existing 2.4 GHz/5 GHz, IEEE 802.11ad has been provided. The IEEE802.11ad is a transmission standard that provides a speed of a maximumof 7 Gbps by using a beamforming technology and is suitable for high bitrate moving picture streaming such as massive data or non-compression HDvideo. However, since it is difficult for the 60 GHz frequency band topass through an obstacle, it is disadvantageous in that the 60 GHzfrequency band can be used only among devices in a short-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

DISCLOSURE Technical Problem

The present invention has been made in an effort to provide ahigh-efficiency/high-performance wireless LAN communication in ahigh-density environment.

In particular, the present invention has been made in an effort toprovide a method for allocating a wideband channel for transmitting datain order to improve communication efficiency.

The present invention has also been made in an effort to guaranteefairness of a communication opportunity between a terminal using thewideband channel and another terminal.

Technical Solution

In order to achieve the objects, the present invention provides awireless communication method and a wireless communication terminal asbelow.

First, an exemplary embodiment of the present invention provides awireless communication method of a terminal, including: obtaining firstprimary channel information of a basic service set (BSS) with which theterminal is associated; performing clear channel assessment (CCA) forone or more secondary channels of the BSS; and setting a second primarychannel among the one or more secondary channels determined to be idlebased on a result of the CCA.

Another exemplary embodiment of the present invention provides awireless communication terminal including: a transceiver transmittingand receiving a radio signal; and a processor controlling an operationof the terminal, wherein the processor obtains first primary channelinformation of a basic service set (BSS) with which the terminal isassociated, performs clear channel assessment (CCA) for one or moresecondary channels of the BSS, and sets a second primary channel amongone or more secondary channels determined to be idle based on a resultof the CCA.

According to an exemplary embodiment, the second primary channel may berandomly set among the one or more idle secondary channels.

According to another exemplary embodiment, a secondary channel, amongthe one or more idle secondary channels, which forms a channel havingthe largest bandwidth in association with another idle secondarychannel(s) may be set as the second primary channel.

According to yet another exemplary embodiment, the second primarychannel may be set based on a frequency interval between each of theidle secondary channels and the first primary channel.

According to still yet another exemplary embodiment, a secondarychannel, among the one or more idle secondary channels, having thehighest order of association with the first primary channel whenapplying a bandwidth extension for wideband data transmission may be setas the second primary channel.

In this case, the first primary channel may be set common to (i.e.identically for) each terminal in the BSS and the second primary channelmay be set independently for each terminal in the BSS.

Next, another exemplary embodiment of the present invention provides awireless communication method of a terminal, including: obtaining firstprimary channel information of a basic service set (BSS) with which theterminal is associated; obtaining second primary channel information setfor the terminal, the second primary channel being set among at leastone of the secondary channels of the BSS; performing a backoff procedurefor the first primary channel; performing clear channel assessment (CCA)for the second primary channel for a predetermined time before a backoffcounter of the backoff procedure is expired; and transmitting data byusing both the first primary channel and the second primary channel whenthe second primary channel is idle as a result of performing the CCA.

Another exemplary embodiment of the present invention provides awireless communication terminal including: a transceiver transmittingand receiving a radio signal; and a processor controlling an operationof the terminal, wherein the processor obtains first primary channelinformation of a basic service set (BSS) with which the terminal isassociated, obtains second primary channel information set for theterminal, in which the second primary channel is set among at least oneof the secondary channels of the BSS, performs a backoff procedure forthe first primary channel, performs clear channel assessment (CCA) forthe second primary channel for a predetermined time before a backoffcounter of the backoff procedure is expired and transmits data by usingboth the first primary channel and the second primary channel when thesecond primary channel is idle as a result of performing the CCA.

In this case, clear channel assessment (CCA) for secondary channels ofthe BSS may be further performed for a predetermined time before thebackoff counter of the backoff procedure is expired and when the secondprimary channel is idle and at least one idle secondary channel whichcan be associated with the second primary channel is present as a resultof performing the CCA, the data may be transmitted through a widebandchannel in which the second primary channel and the idle secondarychannel are associated with each other.

Next, yet another exemplary embodiment of the present invention providesa wireless communication method of a terminal, including: obtainingfirst primary channel information of a basic service set (BSS) withwhich the terminal is associated; obtaining second primary channelinformation set for the terminal, the second primary channel being setamong at least one of the secondary channels of the BSS; performing abackoff procedure for each of the first primary channel and the secondprimary channel; and transmitting data by using at least one channelbetween the first primary channel and the second primary channel inwhich a backoff counter of the backoff procedure is expired.

Yet another exemplary embodiment of the present invention provides awireless communication terminal including: a transceiver transmittingand receiving a radio signal; and a processor controlling an operationof the terminal, wherein the processor obtains first primary channelinformation of a basic service set (BSS) with which the terminal isassociated, obtains second primary channel information set for theterminal, in which the second primary channel is set among at least oneof the secondary channels of the BSS, performs a backoff procedure foreach of the first primary channel and the second primary channel andtransmits data by using at least one channel between the first primarychannel and the second primary channel in which a backoff counter of thebackoff procedure is expired.

According to an exemplary embodiment, a second backoff counter for thebackoff procedure of the second primary channel may be set equal to afirst backoff counter for the backoff procedure of the first primarychannel.

In this case, when the backoff procedure of the first primary channel issuspended, the backoff procedure of the second primary channel may besimultaneously suspended during the suspension period of the backoffprocedure of the first primary channel and when the second primarychannel is continuously maintained to be idle while the backoffprocedure of the second primary channel is performed, the data may betransmitted by using the second primary channel.

According to another exemplary embodiment, each of a first backoffcounter for the backoff procedure of the first primary channel and asecond backoff counter for the backoff procedure of the second primarychannel may be set independently from each other.

In this case, when the second backoff counter is expired earlier thanthe first backoff counter, the terminal may defer transmitting the databy using the second primary channel until the first backoff counter isexpired and when the first backoff counter is expired, the terminal maytransmit the data by using both the first primary channel and the secondprimary channel.

According to yet another exemplary embodiment, the backoff procedure ofthe first primary channel and the backoff procedure of the secondprimary channel may be performed by using a common backoff counter, andthe common backoff counter may be suspended when both the first primarychannel and the second primary channel are busy.

In this case, when the common backoff counter is expired, the data maybe transmitted by using at least one channel between the first primarychannel and the second primary channel which is idle.

According to the exemplary embodiment, the clear channel assessment(CCA) for secondary channels of the BSS may be further performed for apredetermined time before the backoff counter of the backoff procedureof the second primary channel is expired and when at least one idlesecondary channel which can be associated with the second primarychannel is present as a result of performing the CCA, the data may betransmitted through a wideband channel in which the second primarychannel and the idle secondary channel are associated with each other.

Still yet another exemplary embodiment of the present invention providesa wireless communication method of a terminal, including: obtainingfirst primary channel information of a basic service set (BSS) withwhich the terminal is associated; performing clear channel assessment(CCA) for at least one secondary channel of the BSS; and when at leastone idle secondary channel which can be associated with the primarychannel is present as a result of performing the CCA, transmitting thedata through a wideband channel in which the primary channel and theidle secondary channel are associated with each other, wherein atransmission opportunity (TXOP) of the data which is transmitted throughthe associated wideband channel is adjusted based on a bandwidth of thewideband channel.

Still yet another exemplary embodiment of the present invention providesa wireless communication terminal including: a transceiver transmittingand receiving a radio signal; and a processor controlling an operationof the terminal, wherein the processor obtains first primary channelinformation of a basic service set (BSS) with which the terminal isassociated, performs clear channel assessment (CCA) for at least onesecondary channel of the BSS, and when at least one idle secondarychannel which may be associated with the primary channel is present as aresult of performing the CCA, transmits the data through a widebandchannel in which the primary channel and the idle secondary channel areassociated with each other, wherein a transmission opportunity (TXOP) ofthe data which is transmitted through the associated wideband channel isadjusted based on a bandwidth of the wideband channel.

In this case, as the bandwidth of the wideband channel is larger, theadjusted TXOP may be set to be a smaller value.

Still yet another exemplary embodiment of the present invention providesa wireless communication method of a terminal, including: obtainingfirst primary channel information of a basic service set (BSS) withwhich the terminal is associated; obtaining secondary channelinformation forming a wideband channel together with the primary channelfor data transmission of the terminal; allocating a backoff counter forperforming a backoff procedure for the primary channel; and performingthe backoff procedure for the primary channel by using the allocatedbackoff counter, wherein the backoff counter is allocated based on abandwidth of the wideband channel.

Still yet another exemplary embodiment of the present invention providesa wireless communication terminal including: a transceiver transmittingand receiving a radio signal; and a processor controlling an operationof the terminal, wherein the processor obtains first primary channelinformation of a basic service set (BSS) with which the terminal isassociated, obtains secondary channel information forming a widebandchannel together with the primary channel for data transmission of theterminal, allocates a backoff counter for performing a backoff procedurefor the primary channel, and performs the backoff procedure for theprimary channel by using the allocated backoff counter, wherein thebackoff counter is allocated based on a bandwidth of the widebandchannel.

According to an exemplary embodiment, as the bandwidth of the widebandchannel is larger, at least one of a minimum value and a maximum valueof a contention window for allocating the backoff counter may beincreased.

According to another exemplary embodiment, when the terminal transmitsthe data by using the wideband channel, the terminal may extract aplurality of backoff counter candidate values within the set contentionwindow range and allocate the largest value among the extracted backoffcounter candidate values to the backoff counter.

Advantageous Effects

According to exemplary embodiments of the present invention, anenvironment in which a terminal can use a wideband channel is providedby various methods to increase a data transmission speed of theterminal.

According to the exemplary embodiments of the present invention, abandwidth is extended by using a separately allocated alternativeprimary channel in addition to a primary channel allocated to a BSS inthe related art to increase the overall channel use rate.

According to the exemplary embodiments of the present invention, whenthe terminal transmits data by using the wideband channel, fairness of adata transmission opportunity with terminals of another BSS can bemaintained.

According to the exemplary embodiments of the present invention, thetotal resource use rate can be increased in a contention based channelaccess system and performance of a wireless LAN system can be improved.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a diagram illustrating a wireless LAN system according toanother embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a diagram schematically illustrating a process in which a STAand an AP set a link.

FIG. 6 is a diagram illustrating a carrier sense multiple access(CSMA)/collision avoidance (CA) method used in wireless LANcommunication.

FIG. 7 is a diagram illustrating a method for performing a distributedcoordination function (DCF) using a request to send (RTS) frame and aclear to send (CTS) frame.

FIG. 8 is a diagram illustrating a wideband allocation method forwireless LAN communication.

FIG. 9 is a diagram illustrating an exemplary embodiment of a widebandaccess method of a terminal.

FIG. 10 is a diagram illustrating another exemplary embodiment of awideband access method of a terminal.

FIG. 11 is a diagram illustrating yet another exemplary embodiment of awideband access method of a terminal.

FIGS. 12 to 15 are diagrams illustrating methods for setting analternative primary channel according to an exemplary embodiment of thepresent invention.

FIGS. 16 to 23 are diagrams illustrating various methods for operatingan alternative primary channel according to an exemplary embodiment ofthe present invention.

FIGS. 24 to 26 are diagrams illustrating various methods fortransmitting data when a terminal uses a wideband channel according toan exemplary embodiment of the present invention.

BEST MODE

Terms used in the specification adopt general terms which are currentlywidely used by considering functions in the present invention, but theterms may be changed depending on an intention of those skilled in theart, customs, and emergence of new technology. Further, in a specificcase, there is a term arbitrarily selected by an applicant and in thiscase, a meaning thereof will be described in a corresponding descriptionpart of the invention. Accordingly, it should be revealed that a termused in the specification should be analyzed based on not just a name ofthe term but a substantial meaning of the term and contents throughoutthe specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “coupled” to another element, the elementmay be “directly coupled” to the other element or “electrically coupled”to the other element through a third element. Further, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof stated elements but not the exclusion of any other elements.Moreover, limitations such as “or more” or “or less” based on a specificthreshold may be appropriately substituted with “more than” or “lessthan”, respectively.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0063356, 10-2014-0063359 and 10-2014-0148477filed in the Korean Intellectual Property Office and the embodiments andmentioned items described in the respective applications are included inthe Detailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a radio medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, as a concept including allwireless LAN communication devices such as the station and the AP, aterm ‘terminal’ may be used. A station for wireless communicationincludes a processor and a transceiver and according to the embodiment,may further include a user interface unit and a display unit. Theprocessor may generate a frame to be transmitted through a wirelessnetwork or process a frame received through the wireless network andbesides, perform various processing for controlling the station. Inaddition, the transceiver is functionally connected with the processorand transmits and receives frames through the wireless network for thestation.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2, duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a radio signal such asa wireless LAN packet, or the like and may be embedded in the station100 or provided as an exterior. According to the embodiment, thetransceiver 120 may include at least one transmit/receive module usingdifferent frequency bands. For example, the transceiver 120 may includetransmit/receive modules having different frequency bands such as 2.4GHz, 5 GHz, and 60 GHz. According to an embodiment, the station 100 mayinclude a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the AP or an external station according to a wirelessLAN standard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 120 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of transmit/receive modules, each transmit/receive module maybe implemented by independent elements or a plurality of modules may beintegrated into one chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 controls various operations of radio signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality oftransmit/receive modules using different frequency bands. That is, theAP 200 according to the embodiment of the present invention may includetwo or more transmit/receive modules among different frequency bands,for example, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200may include a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the station according to a wireless LAN standard of afrequency band supported by the corresponding transmit/receive module.The transceiver 220 may operate only one transmit/receive module at atime or simultaneously operate multiple transmit/receive modulestogether according to the performance and requirements of the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 controls variousoperations such as radio signal transmission/reception of the AP 200according to the embodiment of the present invention. A detailedembodiment thereof will be described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

FIG. 6 is a diagram illustrating a carrier sense multiple access(CSMA)/collision avoidance (CA) method used in wireless LANcommunication.

A terminal that performs a wireless LAN communication checks whether achannel is busy by performing carrier sensing before transmitting data.When a radio signal having a predetermined strength or more is sensed,it is determined that the corresponding channel is busy and the terminaldelays the access to the corresponding channel. Such a process isreferred to as clear channel assessment (CCA) and a level to decidewhether the corresponding signal is sensed is referred to as a CCAthreshold. When a radio signal having the CCA threshold or more, whichis received by the terminal, indicates the corresponding terminal as areceiver, the terminal processes the received radio signal. Meanwhile,when a radio signal is not sensed in the corresponding channel or aradio signal having a strength smaller than the CCA threshold is sensed,it is determined that the channel is idle.

When it is determined that the channel is idle, each terminal havingdata to be transmitted performs a backoff procedure after an interframespace (IFS) time depending on a situation of each terminal, forinstance, an arbitration IFS (AIFS), a PCF IFS (PIFS), or the likeelapses. According to the embodiment, the AIFS may be used as acomponent which substitutes for the existing DCF IFS (DIFS). Eachterminal stands by while decreasing slot time(s) as long as a randomnumber allocated to the corresponding terminal during an interval of anidle state of the channel and a terminal that completely exhausts theslot time(s) attempts to access the corresponding channel. As such, aninterval in which each terminal performs the backoff procedure isreferred to as a contention window interval.

When a specific terminal successfully accesses the channel, thecorresponding terminal may transmit data through the channel. However,when the terminal which attempts the access collides with anotherterminal, the terminals which collide with each other are allocated withnew random numbers, respectively to perform the backoff procedure again.According to an embodiment, a random number newly allocated to eachterminal may be decided within a range (2*CW) which is twice larger thana range (a contention window, CW) of a random number which thecorresponding terminal is previously allocated with. Meanwhile, eachterminal attempts the access by performing the backoff procedure againin a next contention window interval and in this case, each terminalperforms the backoff procedure from slot time(s) which remained in theprevious contention window interval. By such a method, the respectiveterminals that perform the wireless LAN communication may avoid a mutualcollision for a specific channel.

FIG. 7 is a diagram illustrating a method for performing a distributedcoordination function using a request to send (RTS) frame and a clear tosend (CTS) frame.

The AP and STAs in the BSS contend in order to obtain an authority fortransmitting data. When data transmission at the previous step iscompleted, each terminal having data to be transmitted performs abackoff procedure while decreasing a backoff counter (alternatively, abackoff timer) of a random number allocated to each terminal after anAFIS time. A transmitting terminal in which the backoff counter isexpired transmits the request to send (RTS) frame to notify thatcorresponding terminal has data to transmit. According to an exemplaryembodiment of FIG. 7, STA1 which holds a lead in contention with minimumbackoff may transmit the RTS frame after the backoff counter is expired.The RTS frame includes information on a receiver address, a transmitteraddress, and duration. A receiving terminal (i.e., the AP in FIG. 7)that receives the RTS frame transmits the clear to send (CTS) frameafter waiting for a short IFS (SIFS) time to notify that the datatransmission is available to the transmitting terminal STA1. The CTSframe includes the information on a receiver address and duration. Inthis case, the receiver address of the CTS frame may be set identicallyto a transmitter address of the RTS frame corresponding thereto, thatis, an address of the transmitting terminal STA1.

The transmitting terminal STA1 that receives the CTS frame transmits thedata after a SIFS time. When the data transmission is completed, thereceiving terminal AP transmits an acknowledgment (ACK) frame after aSIFS time to notify that the data transmission is completed. When thetransmitting terminal receives the ACK frame within a predeterminedtime, the transmitting terminal regards that the data transmission issuccessful. However, when the transmitting terminal does not receive theACK frame within the predetermined time, the transmitting terminalregards that the data transmission is failed. Meanwhile, adjacentterminals that receive at least one of the RTS frame and the CTS framein the course of the transmission procedure set a network allocationvector (NAV) and do not perform data transmission until the set NAV isterminated. In this case, the NAV of each terminal may be set based on aduration field of the received RTS frame or CTS frame.

In the course of the aforementioned data transmission procedure, whenthe RTS frame or CTS frame of the terminals is not normally transferredto a target terminal (i.e., a terminal of the receiver address) due to asituation such as interference or a collision, a subsequent process issuspended. The transmitting terminal STA1 that transmitted the RTS frameregards that the data transmission is unavailable and participates in anext contention by being allocated with a new random number. In thiscase, the newly allocated random number may be determined within a range(2*CW) twice larger than a previous predetermined random number range (acontention window, CW).

FIG. 8 illustrates a wideband allocation method for wireless LANcommunication. In FIG. 8 and drawings given below, CH1 to CH8 represent20 MHz channels, respectively, but the number of channels and abandwidth of the channels may be changed according to a communicationscheme to which the present invention is applied.

In the wireless LAN system, the terminals of each BSS performcommunication by setting a specific channel as a primary channel. Theprimary channel is a channel used for non-AP STAs to be associated withthe AP and may be extended to 40 MHz, 80 MHz, and the like from basic 20MHz according to a transmission bandwidth. Meanwhile, a secondarychannel is an adjacent channel having the same bandwidth as the primarychannel and forms a channel having a double bandwidth in associationwith the primary channel.

The terminals of the BSS perform clear channel assessment (CCA) withrespect to each channel to check whether the corresponding channel isbusy and perform bandwidth extension based on channel(s) determined tobe idle. That is, by using 20 MHz as a basic bandwidth, the terminal mayextend the transmission bandwidth to 40 MHz, 80 MHz, and 160 MHz byconsidering whether channels adjacent to the primary channel are idle.

In more detail, referring to FIG. 8, CH1 may be set as a primary 20 MHzchannel of the BSS and a total 40 MHz transmission bandwidth having CH1and CH2 as the primary channel and the secondary channel, respectivelymay be used when CH2 adjacent to CH1 is idle. Further, when both CH3 andCH4 adjacent to CH1 and CH2 are idle, a total 80 MHz transmissionbandwidth having CH1 and CH2 as a primary 40 MHz channel and having CH3and CH4 as a secondary 40 MHz channel may be used. Similarly, when allof CH5 to CH8 adjacent to CH1 to CH4 are idle, a total 160 MHztransmission bandwidth having CH1 to CH4 as a primary 80 MHz channel andhaving CH5 to CH8 as a secondary 80 MHz channel may be used.

FIG. 9 illustrates a wideband access method of a terminal using arequest to send (RTS) frame and a clear to send (CTS) frame. In theexemplary embodiment of FIG. 9, a maximum bandwidth is set to 80 MHz inthe corresponding BSS. Further, as described above in FIG. 7, theterminal performs a backoff procedure for the primary channel (CH1) andwhen a backoff counter is expired the terminal transmits RTS frames tochannels (CH1 to CH4) of 80 MHz bandwidth, which include the primarychannel and the secondary channels.

First, FIG. 9(a) illustrates a wideband access method according to adynamic bandwidth operation. Referring to FIG. 9(a), the terminaltransmits the RTS frames to each of the channels CH1 to CH4 of 80 MHzbandwidth, but CTS frames are received only in CH1 and CH2 sincesecondary 40 MHz channels CH3 and CH4 are busy. Therefore, the terminaltransmits data by using a partial bandwidth of 40 MHz as thetransmission bandwidth. In this case, the transmission bandwidth has CH1and CH2 in which the CTS frame is received as the primary channel andthe secondary channel, respectively. Meanwhile, the correspondingterminal may not use CH3 and CH4 in which the CTS frame is not receiveduntil a next backoff procedure for the primary channel CH1 is performed.That is, according to the exemplary embodiment of FIG. 9(a), theterminal transmits data by using the maximum bandwidth when the primarychannel and all secondary channels are idle. Further, the terminaltransmits data by using only a partial bandwidth including the primarychannel when at least some of secondary channels are busy.

Next, FIG. 9(b) illustrates a wideband access method according to astatic bandwidth operation. Referring to FIG. 9(b), the terminaltransmits the RTS frames to each of the channels CH1 to CH4 of 80 MHzbandwidth, but CTS frames are not received through some channels CH3 andCH4 since the CH3 and CH4 are busy. Accordingly, the terminal postponesusing all channels CH1 to CH4 of 80 MHz bandwidth and transmits the RTSframes for four channels again after the next backoff procedure. Thatis, according to the exemplary embodiment of FIG. 9(b), when at leastone channel among all channels of the maximum bandwidth is busy, theterminal does not use the total bandwidth and performs a backoffprocedure again for the primary channel in order to transmit data.

FIG. 10 illustrates another exemplary embodiment of a wideband accessmethod of a terminal. Even in the exemplary embodiment of FIG. 10, themaximum bandwidth is set to 80 MHz in the corresponding BSS andduplicated description with the exemplary embodiment of FIG. 9 will beomitted.

FIG. 10(a) illustrates an exemplary embodiment in which data issuccessfully transmitted by using the set maximum bandwidth, and FIGS.10(b) and 10(c) illustrate exemplary embodiments of data transmission inwhich some channels of the maximum bandwidth are busy. In more detail,FIG. 10(b) illustrates the wideband access method according to thedynamic bandwidth operation and when the secondary 40 MHz channels CH3and CH4 are busy, the terminal transmits data by using only the primary40 MHz channels CH1 and CH2. Next, FIG. 10(c) illustrates the widebandaccess method according to the static bandwidth operation and when atleast some channels are busy, the terminal does not transmit data anddefers by performing a backoff procedure until the maximum bandwidth of80 MHz is totally usable.

Meanwhile, in each exemplary embodiment of FIG. 10, the backoffprocedure and enhanced distributed coordination access (EDCA) areperformed only in the primary 20 MHz channel CH1 and in other secondarychannels CH2 to CH4, it may be verified whether the correspondingchannel is usable through CCA for a PIFS time before the backoff counteris expired.

FIG. 11 illustrates yet another exemplary embodiment of a widebandaccess method of a terminal. In the previous exemplary embodiments, theterminal that transmits the data uses initially set channel(s) until thecorresponding transmission ends, but in the exemplary embodiment of FIG.11, when a channel which is additionally usable is sensed whiletransmitting the data, the terminal may use the corresponding channel.

In more detail, the terminal performs a backoff procedure for theprimary channel CH1 and verifies, in other secondary channels CH2 toCH4, whether each channel is usable by performing CCA for the PIFS timebefore the backoff counter of the backoff procedure is expired. Asdescribed in the exemplary embodiment of FIG. 11, when some secondarychannels CH3 and CH4 are busy, the terminal performs data transmissionby using only the channels CH1 and CH2 of a partial bandwidth, that is,40 MHz bandwidth, which include the primary channel CH1. However, whenthe channels CH3 and CH4 which have been impossible to use at a widebandaccess time become idle and thereby usable while transmitting the data,the terminal may perform additional channel access to the correspondingchannels.

According to the exemplary embodiment of the present invention, theterminal may set at least one channel among the secondary channels whichare usable (i.e., idle) as an alternative primary channel (APCH).Furthermore, the terminal may perform an additional channel access byusing the set alternative primary channel. In the exemplary embodimentof the present invention, the alternative primary channel (APCH) is aprimary channel set in addition to the basic primary channel (i.e.,primary 20 MHz channel) of the corresponding BSS. The alternativeprimary channel may operate as a primary channel for at least onechannel among secondary channels which are not associated with the basicprimary channel. That is, in the aforementioned exemplary embodiment,separate bandwidth extension may be performed based on the alternativeprimary channel similarly to the case where the bandwidth extension forwideband data transmission is performed based on the basic primarychannel. The alternative primary channel may be used for the associationbetween the non-AP STA and the AP similarly to the basic primary channeland the backoff procedure, the enhanced distributed coordination access(EDCA), and the like may be performed. In the same BSS, the basicprimary channel is set identically for each terminal, but thealternative primary channel may be set independently for each terminal.Accordingly, an alternative primary channel set in some terminals may bedifferent from an alternative primary channel set in other terminals inthe same BSS. The non-AP STA may set a new link with the AP by using thealternative primary channel and transmit data through the set link.Meanwhile, in the exemplary embodiment of the present invention, it isdescribed that the basic primary channel is an original primary channelset in the corresponding BSS and has a bandwidth of 20 MHz, but thepresent invention is not limited thereto and the basic primary channelmay be set with another bandwidth in some exemplary embodiments.

FIG. 11 illustrates an exemplary embodiment in which CH3 between theusable secondary channels CH3 and CH4 is set as the alternative primarychannel. When the alternative primary channel CH3 becomes idle, theterminal performs a backoff procedure for CH3 after an xIFS time. ThexIFS in which the terminal waits before the backoff procedure of thealternative primary channel starts may become the aforementioned AIFS orPIFS and the present invention is not limited thereto. Meanwhile, forthe PIFS time before the backoff counter for the alternative primarychannel CH3 is expired, the terminal performs CCA for another secondarychannel CH4 which can be associated with the alternative primary channelCH3 to verify whether the corresponding channel is usable. When thealternative primary channel CH3 is maintained to be idle and the backoffcounter for the corresponding channel is thus expired, the terminaltransmits data by using the alternative primary channel CH3. In thiscase, when the secondary channel CH4 which can be associated with thealternative primary channel CH3 is present by maintaining the idle statefor the PIFS time before the backoff counter is expired, the terminaltransmits data by using a wideband channel in which the alternativeprimary channel CH3 and the corresponding secondary channel CH4 areassociated with each other.

FIGS. 12 to 15 illustrate methods for setting an alternative primarychannel according to an exemplary embodiment of the present invention.

In the exemplary embodiments of FIGS. 12 to 15, a channel marked with ashade represents a channel which is busy. In the exemplary embodiment ofthe present invention, the busy channel includes a channel used fortransmitting data by the corresponding terminal and a channel used fortransmitting data by another terminal. Herein, the channel used fortransmitting data by another terminal may be determined based on a CCAresult of the corresponding channel and include a channel used fortransmitting data by another terminal in the same BSS and a channel inwhich interference occurs due to a transmission signal of a terminal inanother BSS. The terminal obtains basic primary channel information ofthe BSS with which the corresponding terminal is associated and performsCCA with respect to the basic primary channel and secondary channels. Inaddition, the terminal may set the alternative primary channel among oneor more secondary channels determined to be idle as a result ofperforming the CCA.

First, FIG. 12 illustrates a method for setting an alternative primarychannel according to an exemplary embodiment of the present invention.In the exemplary embodiment of FIG. 12, CH1 is set as the basic primarychannel (i.e., primary 20 MHz channel), and CH1 to CH3 are busy, and CH4to CH8 are idle.

According to the exemplary embodiment of FIG. 12, the alternativeprimary channel may be randomly set among usable idle secondarychannels. That is, all idle secondary channels may become candidates ofthe alternative primary channel and the respective secondary channelsmay be selected as the alternative primary channel with a uniformprobability distribution. In the exemplary embodiment of FIG. 12, 5 idlesecondary channels of CH4 to CH8 are present, and therefore, eachsecondary channel may be selected as the alternative primary channelwith a probability of 1/5. Meanwhile, according to an additionalexemplary embodiment of the present invention, a weighted value ofselecting the alternative primary channel for each secondary channel maybe granted according to a channel situation, a traffic characteristic,and the like.

FIG. 13 illustrates a method for setting an alternative primary channelaccording to another exemplary embodiment of the present invention. Inthe exemplary embodiment of FIG. 13, CH1 is set as the basic primarychannel, and CH1 to CH3 and CH5 are busy, and CH4 and CH6 to CH8 areidle.

According to the exemplary embodiment of FIG. 13, a channel, among theusable idle secondary channels, which may form a channel having thelargest bandwidth in association with other secondary channel(s) may beset as the alternative primary channel. In FIG. 13, since CH3 adjacentto CH4 is busy, a formable bandwidth of CH4 becomes a maximum of 20 MHz.Similarly, since CH5 adjacent to CH6 is busy, a formable bandwidth ofCH6 becomes a maximum of 20 MHz. However, since channels CH8 and CH7adjacent to CH7 and CH8, respectively are idle, CH7 and CH8 may formchannels having the larger bandwidth in association with the adjacentchannels and the formable bandwidths of CH7 and CH8 become a maximum of40 MHz. Therefore, according to the exemplary embodiment of FIG. 13, CH7and CH8 having the largest formable bandwidth may become the candidatesof the alternative primary channel.

The terminal may set one of a plurality of secondary channels which mayform the channel having the largest bandwidth as the alternative primarychannel. According to an exemplary embodiment, the terminal may randomlyset the alternative primary channel among the plurality of secondarychannels which may form the channel having the largest bandwidth bycombining the exemplary embodiments of FIGS. 12 and 13. That is, in FIG.13, CH7 and CH8 may become the candidates of the alternative primarychannel and each secondary channel may be selected as the alternativeprimary channel with the probability of 1/2.

FIGS. 14 and 15 illustrate methods for setting an alternative primarychannel according to yet another exemplary embodiment of the presentinvention. In the exemplary embodiment of FIGS. 14 and 15, CH4 is set asthe basic primary channel, and CH3 to CH5 are busy, and CH1, CH2 and CH6to CH8 are idle.

According to the exemplary embodiment of the present invention, thealternative primary channel may be selected based on a frequencyinterval between the corresponding secondary channel and the basicprimary channel among the usable idle secondary channels. FIGS. 14 and15 illustrate an exemplary embodiment in which a secondary channelhaving the smallest frequency interval from the basic primary channel,that is, most adjacent to the basic primary channel is selected as thealternative primary channel. In this case, a method that selects theadjacent channel includes a method based on a physical frequencyinterval and a method based on a logical frequency interval.

First, FIG. 14 illustrates an exemplary embodiment of selecting thealternative primary channel based on the physical frequency interval.The method based on the physical frequency interval means selecting thealternative primary channel by considering only an actual frequencyinterval. Referring to FIG. 14, CH2 and CH6 which are most adjacent tothe basic primary channel CH4, among the idle secondary channels maybecome the candidates of the alternative primary channel. The terminalmay randomly set the alternative primary channel between the alternativeprimary channel candidates CH2 and CH6.

On the contrary, FIG. 15 illustrates an exemplary embodiment ofselecting the alternative primary channel based on the logical frequencyinterval. The logical frequency interval may be determined according toa merging or association order with the primary channel according to theaforementioned wideband allocation rule. Referring to FIG. 15, CH1 andCH2 having the highest order of association with the basic primarychannel CH4 may become the candidates of the alternative primary channelin order to form the wideband channel among the idle secondary channels.According to an exemplary embodiment, the terminal may randomly set thealternative primary channel between the alternative primary channelcandidates CH1 and CH2. According to another exemplary embodiment, theterminal may set the alternative primary channel by using both thelogical frequency interval and the physical frequency interval. That is,CH2 having the smallest physical frequency interval from the basicprimary channel CH4, between CH1 and CH2 having the smallest logicalfrequency interval from CH4 may be set as the alternative primarychannel. Meanwhile, in the exemplary embodiment of FIG. 15, CH6 has thesame physical frequency interval from the basic primary channel as CH2,but since CH6 has the larger logical frequency interval from the basicprimary channel than CH2, and as a result, CH6 is not selected as thealternative primary channel.

According to an additional exemplary embodiment of the presentinvention, a channel having the lowest signal strength according to aresult of performing CCA for each secondary channel may be set as thealternative primary channel. In this case, a channel having smallinterference and noise is set as the alternative primary channel toincrease reliability and efficiency of the data transmission.

The aforementioned methods for setting alternative primary channeldescribe exemplary embodiments of the present invention and thealternative primary channel may be set by combining or modifying theaforementioned exemplary embodiments. For example, the alternativeprimary channel may be selected even by a method opposite to theexemplary embodiments of FIGS. 14 and 15. In other words, the secondarychannel (e.g., CH8) having the largest physical frequency interval orlogical frequency interval from the basic primary channel may be set asthe alternative primary channel. Further, in the exemplary embodiment ofFIG. 13, among channels which may form the channel having the largestbandwidth in association with other secondary channel(s), a channel(e.g., CH7) having the smallest physical frequency interval or logicalfrequency interval from the basic primary channel may be selected as thealternative primary channel.

FIGS. 16 to 23 illustrate various methods for operating an alternateprimary channel according to an exemplary embodiment of the presentinvention. In the respective exemplary embodiments of FIGS. 16 to 23,duplicated description of parts which are the same as or correspond tothe exemplary embodiment of the previous drawing will be omitted.

In the exemplary embodiment of FIGS. 16 to 23, it is assumed that CH1 isset as the basic primary channel (i.e., primary 20 MHz channel) and CH8is set as the alternative primary channel. Each terminal in the BSSobtains basic primary channel information and the alternative primarychannel information and attempts bandwidth extension to secondarychannels adjacent to the basic primary channel and the alternativeprimary channel, respectively. The terminal may transmit data throughthe channels of the secured bandwidth. In the exemplary embodiment ofthe present invention, ‘data’ is used as a term including concepts of adata frame, a PLCP protocol data unit (PPDU), a MAC protocol data unit(MPDU), an aggregate MPDU (A-MPDU), and the like according to theimplementation. Further, in the exemplary embodiment of the presentinvention, a ‘basic channel group’ indicates the basic primary channelitself or a channel having an extended bandwidth, which includes thebasic primary channel. In addition, an ‘alternative channel group’ isused as a term that indicates the alternative primary channel itself ora channel having an extended bandwidth, which includes the alternativeprimary channel.

FIG. 16 illustrates an exemplary embodiment of a PIFS sensing basedalternative primary channel operation method. According to the exemplaryembodiment of FIG. 16, the terminal performs a backoff procedure for thebasic primary channel CH1 in order to transmit data and performs CCA forthe alternative primary channel CH8 for a PIFS time before the backoffcounter of the backoff procedure is expired to verify whether thecorresponding channel is usable. In this case, for the PIFS time beforethe backoff counter is expired, the terminal may perform CCA even withrespect to other secondary channels CH2 to CH7 in addition to thealternative primary channel CH8.

When the basic primary channel CH1 is maintained to be idle and thebackoff counter for the corresponding channel is thus expired, theterminal transmits data through the basic channel group including thebasic primary channel CH1. In order to set the basic channel group, theterminal performs the bandwidth extension based on the CCA result ofeach secondary channel performed for the PIFS time before the backoffcounter for the basic primary channel is expired. Referring to FIG. 16,the secondary 20 MHz channel CH2 of the basic primary channel CH1 isidle for the PIFS time before the backoff counter for the basic primarychannel CH1 is expired, but CH4 among secondary 40 MHz channels is busy.Therefore, the terminal sets CH1 and CH2 as the basic channel group andtransmits data through the channel having the 40 MHz bandwidth.

According to the exemplary embodiment of the present invention, when thealternative primary channel CH8 is idle for the PIFS time, the terminaltransmits the data even through the alternative channel group includingthe alternative primary channel CH8. In order to set the alternativechannel group, the terminal performs the bandwidth extension based onthe CCA result of each secondary channel performed for the PIFS timebefore the backoff counter for the basic primary channel is expired.That is, when secondary channel(s) which can be associated with thealternative primary channel CH8 is present by maintaining the idle statefor the PIFS time before the backoff counter is expired, the terminaltransmits data by using the wideband channel in which the alternativeprimary channel CH8 and the corresponding secondary channel(s) areassociated with each other. Referring to FIG. 16, the secondary 20 MHzchannel CH7 of the alternative primary channel CH8 and the secondary 40MHz channels CH5 and CH6 are all idle for the PIFS time. Therefore, theterminal sets CH5 to CH8 as the alternative channel group to transmitthe data through the channel having the 80 MHz bandwidth.

Meanwhile, according to another exemplary embodiment of the presentinvention, the terminal may perform a separate backoff procedure for thealternative primary channel to determine whether the correspondingchannel is usable. In the exemplary embodiments given below, the backoffprocedure for the alternative primary channel is performed to maintainfairness of channel use, while it is determined whether the alternativeprimary channel is usable only by the CCA for the PIFS time in theexemplary embodiment of FIG. 16.

FIGS. 17 to 19 illustrate an exemplary embodiment of a common backoffbased alternative primary channel operation method. That is, accordingto the exemplary embodiment of FIGS. 17 to 19, the backoff counter setin the basic primary channel CH1 is shared as the backoff counter forthe alternative primary channel CH8. When the alternative primarychannel CH8 is idle until the common backoff counter is expired, theterminal may transmit data through the alternative channel groupincluding the alternative primary channel CH8.

FIG. 17 illustrates an exemplary embodiment in which while the backoffprocedure for each of the basic primary channel CH1 and the alternativeprimary channel CH8 is performed, both channels are idle. When the basicprimary channel CH1 and the alternative primary channel CH8 are allmaintained to be idle and the backoff counter is thus expired, theterminal transmits data by using both the basic channel group and thealternative channel group. In this case, based on the CCA result foreach of the secondary channels for the PIFS time before the backoffcounter is expired, the terminal performs the bandwidth extension basedon the basic primary channel CH1 and the bandwidth extension based onthe alternative primary channel CH8. Accordingly, in the exemplaryembodiment of FIG. 17, the terminal transmits the data by using thebasic channel group having the 40 MHz bandwidth and the alternativechannel group having the 80 MHz bandwidth.

FIG. 18 illustrates an exemplary embodiment in which while the backoffprocedure for each of the basic primary channel CH1 and the alternativeprimary channel CH8 is performed, the basic primary channel CH1 is busy.According to the exemplary embodiment of FIG. 18, when the basic primarychannel CH1 is busy, the terminal suspends the backoff procedures forthe basic primary channel CH1 and the alternative primary channel CH8.When the busy state of the basic primary channel CH1 ends, the terminalresumes the backoff procedures for the basic primary channel CH1 and thealternative primary channel CH8 after an AIFS time. That is, in theexemplary embodiment of FIG. 18, the backoff procedure of thealternative primary channel CH8 is performed dependently to the backoffprocedure of the basic primary channel CH1. Therefore, when the backoffprocedure of the basic primary channel CH1 is suspended, the terminalalso suspends the backoff procedure of the alternative primary channelCH8. In addition, when the backoff procedure of the basic primarychannel CH1 is resumed, the terminal also resumes the backoff procedureof the alternative primary channel CH8. When the alternative primarychannel CH8 is maintained to be idle while the backoff procedure isperformed, the terminal transmits data by using both the basic channelgroup and the alternative channel group after the backoff counter isexpired. Accordingly, in the exemplary embodiment of FIG. 18, theterminal transmits the data by using the basic channel group having the40 MHz bandwidth and the alternative channel group having the 80 MHzbandwidth.

FIG. 19 illustrates an exemplary embodiment in which while the backoffprocedure for each of the basic primary channel CH1 and the alternativeprimary channel CH8 is performed, the alternative primary channel CH8 isbusy. Referring to FIG. 19, the backoff procedure of the alternativeprimary channel CH8 is performed dependently to the backoff procedure ofthe basic primary channel CH1, but the backoff procedure of the basicprimary channel CH1 may be performed independently from the backoffprocedure of the alternative primary channel CH8. That is, when thealternative primary channel CH8 is busy, the backoff procedure of thealternative primary channel CH8 is suspended, but the backoff procedureof the basic primary channel CH1 is continuously performed withoutsuspension. As described above, when the backoff procedure of the basicprimary channel CH1 is expired, the terminal may transmit the datathrough the basic channel group including the basic primary channel CH1.However, the data is not transmitted through the alternative primarychannel CH8 in which the interference occurs during the backoffprocedure. Accordingly, in the exemplary embodiment of FIG. 19, theterminal transmits the data by using the basic channel group having the40 MHz bandwidth.

FIGS. 20 and 21 illustrate an exemplary embodiment of an independentbackoff based alternative primary channel operation method. That is,according to the exemplary embodiment of FIGS. 20 and 21, the backoffcounter for the basic primary channel CH1 and the backoff counter forthe alternative primary channel CH8 are set independently from eachother. Therefore, a backoff counter value allocated to the alternativeprimary channel CH8 may be larger or smaller than a backoff countervalue allocated to the basic primary channel CH1.

FIG. 20 illustrates an exemplary embodiment in which the backoff counterfor the alternative primary channel CH8 is expired earlier than thebackoff counter for the basic primary channel CH1. When the backoffcounter for the alternative primary channel CH8 is expired earlier, theterminal switches the alternative primary channel CH8 to an APCH readystate. In the APCH ready state, the terminal defers the datatransmission using the alternative primary channel CH8 until the backoffcounter for the basic primary channel CH 1 is expired. When the backoffcounter for the basic primary channel CH1 is expired in the APCH readystate and the alternative primary channel CH8 is maintained to be idleuntil the corresponding time, the terminal transmits the data by usingboth the basic channel group and the alternative channel group. In thiscase, based on the CCA result for each of the secondary channels for thePIFS time before the backoff counter for the basic primary channel CH1is expired, the terminal performs the bandwidth extension based on thebasic primary channel CH1 and the bandwidth extension based on thealternative primary channel CH8. Accordingly, in the exemplaryembodiment of FIG. 20, the terminal transmits the data by using thebasic channel group having the 40 MHz bandwidth and the alternativechannel group having the 80 MHz bandwidth.

Meanwhile, when the interference occurs in the alternative primarychannel CH8 in the APCH ready state and thus the corresponding channelbecomes busy, the terminal cancels the APCH ready state. In this case,the terminal is allocated with a new backoff counter for the alternativeprimary channel CH8 and performs a backoff procedure for the alternativeprimary channel CH8 by using the new backoff counter when the busy stateof the alternative primary channel CH8 ends.

FIG. 21 illustrates an exemplary embodiment in which the backoff counterfor the basic primary channel CH1 is expired earlier than the backoffcounter for the alternative primary channel CH8. When the backoffcounter for the basic primary channel CH1 is expired earlier, theterminal transmits the data by using only the basic channel group.However, the data is not transmitted through the alternative primarychannel CH8 in which the backoff counter is not expired. Accordingly, inthe exemplary embodiment of FIG. 21, the terminal transmits the data byusing the basic channel group having the 40 MHz bandwidth. According toan exemplary embodiment of the present invention, when the backoffcounter for the basic primary channel CH1 is expired, the backoffcounter for the alternative primary channel CH8 may be suspended whilethe data is transmitted through the basic primary channel CH1.

Meanwhile, according to yet another exemplary embodiment of the presentinvention, the terminal may transmit the data through the alternativeprimary channel independently regardless of whether the data istransmitted through the basic primary channel. That is, even when thebasic primary channel is busy and the terminal may not thus use thebasic primary channel, the terminal may transmit the data by using thealternative primary channel.

FIG. 22 illustrates an exemplary embodiment of independently using thealternative primary channel. According to the exemplary embodiment ofFIG. 22, the backoff procedures are performed for the basic primarychannel CH1 and the alternative primary channel CH8 by using the commonbackoff counter and in the backoff procedures of each channel, thecommon backoff counter is suspended only when both the basic primarychannel CH1 and the alternative primary channel CH8 are busy. However,when at least one of the basic primary channel CH1 and the alternativeprimary channel CH8 is idle, the common backoff counter is resumed. Theterminal may transmit the data by using the primary channel(s) which isidle when the common backoff counter is expired. That is, when both thebasic primary channel CH1 and the alternative primary channel CH8 areidle, the terminal transmits the data by using both the basic channelgroup and the alternative channel group. In addition, when only any oneof both channels is idle, the terminal transmits the data only throughthe channel group including the idle primary channel.

Referring to FIG. 22, the alternative primary channel CH8 becomes busyearlier while the backoff procedures for the basic primary channel CH1and the alternative primary channel CH8 are performed, but since thebasic primary channel CH1 is idle, the common backoff counter is notsuspended. However, when the basic primary channel CH1 becomesadditionally busy so that both channels CH1 and CH8 become busy, thecommon backoff counter is suspended. According to the exemplaryembodiment of FIG. 22, while the common backoff counter is suspended,the alternative primary channel CH8 returns to be idle again and thecommon backoff counter is resumed again after an AIFS time. When thecommon backoff counter is expired, the basic primary channel CH1 isbusy, while the alternative primary channel CH8 is idle. Therefore, theterminal transmits the data by using the alternative channel groupincluding the idle alternative primary channel CH8.

FIG. 23 illustrates another exemplary embodiment of independently usingthe alternative primary channel. According to the exemplary embodimentof FIG. 23, the backoff procedure of the alternative primary channel CH8may be performed independently from the backoff procedure of the basicprimary channel CH1. In this case, the backoff counter for thealternative primary channel CH8 may be set equal to the backoff counterfor the basic primary channel CH1. Alternatively, the backoff counterfor the alternative primary channel CH8 may be set as a separate backoffcounter.

That is, in the exemplary embodiment of FIG. 23, the terminal isseparately allocated with a first backoff counter (i.e. timer) for thebasic primary channel CH1 and a second backoff counter (i.e. timer) forthe alternative primary channel CH8. In this case, the terminal mayperform the backoff procedures for the respective primary channels CH1and CH8 by using the allocated individual backoff counters. Referring toFIG. 23, the terminal performs the backoff procedure for the basicprimary channel CH1 by using the first backoff counter and suspends thefirst backoff counter when the basic primary channel CH1 is busy.Similarly, the terminal performs the backoff procedure for thealternative primary channel CH8 by using the second backoff counter andsuspends the second backoff counter when the alternative primary channelCH8 is busy. As illustrated in FIG. 23, while the second backoff counteris suspended, the alternative primary channel CH8 returns to be idleagain and the terminal resumes the second backoff counter after an AIFStime. When the second backoff counter is expired, the terminal transmitsthe data by using the alternative channel group including thealternative primary channel CH8.

The aforementioned exemplary embodiments of the present invention may beused for data transmission of the terminal through combination withOrthogonal Frequency Division Multiple Access (OFDMA). That is, thechannels secured by the aforementioned exemplary embodiments may beallocated to one terminal, but alternatively allocated to a plurality ofterminals in a wireless LAN system to which the OFDMA is applied.

Meanwhile, when the terminal uses the wideband channel through thebandwidth extension in a dense BSS environment as described above,channel access opportunities of other adjacent BSS terminals may bedeprived. Therefore, when the terminal intends to transmit the data byusing the wideband channel, a method for maintaining the fairness of thedata transmission opportunity with the other BSS terminals is required.

FIGS. 24 to 26 are diagrams illustrating various methods fortransmitting data when a terminal uses a wideband channel according toan exemplary embodiment of the present invention. In the exemplaryembodiment of FIGS. 24 to 26, CH1 is set as the primary channel andduplicated description of parts which are the same as or correspond tothe aforementioned exemplary embodiment will be omitted.

First, FIG. 24 is a diagram illustrating an exemplary embodiment of adata transmitting method using the wideband channel. According to theexemplary embodiment of FIG. 24, when the terminal transmits the data byusing the wideband channel, the terminal may adjust a transmissionopportunity (TXOP) of the corresponding data. The TXOP means aguaranteed time for a terminal to continuously transmit packet(s).According to an exemplary embodiment, when the terminal transmits thedata through the wideband channel including a plurality of basicchannels, the terminal may transmit the data based on TXOP′ (i.e.adjusted TXOP) having a smaller value than an original TXOP. In thiscase, the basic channel may represent a channel having a basic bandwidth(e.g., 20 MHz) set for a data transmission.

As described in the aforementioned exemplary embodiment, the terminalwhich intends to transmit the data performs the backoff procedure forthe primary channel CH1 and performs the CCA for the secondary channelsCH2 to CH4 for the PIFS time before the backoff counter of the backoffprocedure is expired to determine whether each channel is usable. Whenat least one idle secondary channel which can be associated with theprimary channel CH1 is present, the terminal transmits the data throughthe wideband channel in which the primary channel CH1 and the idlechannel is associated with each other. In this case, the terminal maytransmit the data based on the adjusted TXOP (i.e., TXOP′).

Table 1 shows Enhanced Distributed Coordination Access (EDCA) parametervalues set according to an access category (AC). In Table 1, the accesscategory includes an access category AC_BK of a background state, anaccess category AC_BE of a best effort state, an access category AC_VIof video data, an access category AC_VO of voice data, and a legacydistributed coordination function (DCF). Further, the parameters includea minimum value CWmin of a contention window, a maximum value CWmax of acontention window, an AIFS value AIFSN, a maximum TXOP, and the adjustedTXOP (i.e. TXOP′).

TABLE 1 Max AC CWmin CWmax AIFSN TXOP TXOP′ Background 15 1023 7 0 A′(AC_BK) Best Effort 15 1023 3 0 A′ (AC_BE) Video 7 15 2 3.008 ms B′ <3.008 ms (AC_VI) Voice 3 7 2 1.504 ms B′ < 1.504 ms (AC_VO) Legacy DCF15 1023 2 0 A′

As shown in Table 1, a TXOP′ of data transmitted through the widebandchannel may be determined to be a predetermined value A′ or a value B′smaller than an original TXOP in the corresponding access category.According to an exemplary embodiment of the present invention, the TXOP′of the data transmitted through the associated wideband channel may havea relationship with the predetermined TXOP as shown in an equation givenbelow.

TXOP′=β TXOP  [Equation 1]

Where, β is a constant value which is inverse proportional to the numberof basic channels occupied by the corresponding terminal. For example,if the bandwidth of the basic channel is 20 MHz, β is set to ½ when theterminal transmits data with the bandwidth of 40 MHz, and β may be setto ⅓ when the terminal transmits data with the bandwidth of 60 MHz. Thatis, when the terminal transmits data by using a bandwidth which is ntimes larger than the basic channel, the TXOP′ value may be adjusted to1/n of the predetermined TXOP. However, in the present invention, amethod for setting the TXOP′ is not limited thereto and as the bandwidthof the wideband channel used by the terminal is larger, the TXOP′ may beset to a smaller value.

According to an additional exemplary embodiment of the presentinvention, secondary channel(s) separated from the primary channel inaddition to secondary channel(s) adjacent to the primary channel may beassociated with the primary channel to be used for transmitting thedata. In this case, the bandwidth which can be occupied by the terminalmay be set to a value which is integer times larger than the basicchannel as 20 MHz, 40 MHz, 60 MHz, 80 MHz, 100 MHz, 120 MHz, 140 MHz,160 MHz, and the like. Similarly even in this case, the terminal may setthe TXOP′ of the data based on the number of secondary channelsassociated with the primary channel. That is, as the number of secondarychannels associated with the primary channel is larger, the TXOP′ may beset to be smaller. Meanwhile, according to another exemplary embodiment,a channel having the smaller bandwidth than the basic channel may beused for the data transmission according to a design of thecommunication system. When the data is transmitted through a channelhaving the smaller bandwidth than the basic channel as described above,β is set to a value larger than 1 to allocate a TXOP′ having the largervalue than the predetermined TXOP to the corresponding data.

Meanwhile, according to the exemplary embodiment of the presentinvention, f3 which is a constant for determining the TXOP′ may bedetermined by reflecting an additional weighted value as well as thewideband channel used by terminal. According to an exemplary embodiment,the terminal may determine an available situation of the channel byusing information such as a control frame received during apredetermined interval before the present time, and the like and adjustthe weighed value for the constant β based on the determined channelavailable situation. The weighted value may determine a change amount ofthe TXOP′ depending on a change in the number of basic channels occupiedby the terminal. For example, the weighted value may be determined as1/β under a situation in which the terminal may sufficiently exclusivelyoccupy the wideband channel and in this case, the TXOP′ depending on theuse of the wideband channel may be set to the same value as the originalTXOP.

FIG. 25 illustrates another exemplary embodiment of the datatransmitting method using the wideband channel. According to theexemplary embodiment of FIG. 25, when the terminal transmits the data byusing the wideband channel, the terminal may increase the size of thebackoff counter used in the backoff procedure of the correspondingterminal.

As described above, the backoff counter for the backoff procedure of theprimary channel is determined as the random number value within thecontention window (CW) range set in the corresponding terminal. Herein,the contention window (CW) of each terminal is determined between theminimum value CWmin of the contention window and the maximum value CWmaxof the contention window. That is, the contention window (CW) of eachterminal is initialized to the minimum value CWmin of the contentionwindow and a terminal in which a collision occurs in the backoffprocedure increases the contention window (CW) in a range within themaximum value CWmax of the contention window (for example, two timeslarger than the previous contention window). As the contention window(CW) set for the terminal increases, the corresponding terminal has thehigher probability to be allocated with the backoff counter having thelarger value.

According to an exemplary embodiment of the present invention, when theterminal transmits data by using the wideband channel, the value of thecontention window (CW) set for the corresponding terminal may increase.For example, the minimum value CWmin of the contention window and themaximum value CWmax of the contention window may be basically set asenumerated in Table 1 according to a traffic type. In this case, as thebandwidth of the wideband channel used by the terminal increases, atleast one of the minimum value CWmin of the contention window and themaximum value CWmax of the contention window set for the correspondingterminal may increase.

According to another exemplary embodiment of the present invention, whenthe terminal transmits the data by using the wideband channel, thecorresponding terminal may extract a plurality of backoff countercandidate values within the set contention window (CW) range andallocate the largest value among the extracted backoff counter candidatevalues to the backoff counter for the corresponding terminal. Forexample, when the terminal transmits the data by using the bandwidthwhich is n times larger than the basic channel, n backoff countercandidate values may be randomly extracted within the contention window(CW) range set for the corresponding terminal. In this case, theterminal may set the largest value among n extracted backoff countercandidate values as the backoff counter for the primary channel of thecorresponding terminal.

A probability that a value z will be randomly extracted within the setcontention window value CW is 1/CW. However, as described above, f(z)which is a probability that n values being randomly extracted within thecontention window value CW and z become the largest value among nextracted values is shown in an equation given below.

$\begin{matrix}{{f(z)} = {\frac{n}{CW}( \frac{z}{CW} )^{n - 1}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

Accordingly, as n which is the number of times of extracting the backoffcounter candidate value increases, a probability that z which is thelargest value among the backoff counter candidate values will become avalue close to the contention window value CW increases.

Meanwhile, the terminal may determine an available situation of thechannel by using the information such as the control frame receivedduring the predetermined interval before the present time, and the likeand adjust the increase probability of the backoff counter based on thedetermined channel available situation. For example, the terminal maydecrease an increase amount of the contention window (CW) value set forthe corresponding terminal as the channel available situation is better.To this end, the terminal may decrease the increase amounts of theminimum value CWmin of the contention window and the maximum value CWmaxof the contention window. Similarly, the terminal may decrease n whichis the number of times of extracting the backoff counter candidate valuefor the corresponding terminal as the channel available situation isbetter. As such, when the channel available situation is better, anunnecessary backoff procedure in a non-contention state may be preventedby decreasing the increase amount of the contention window (CW) and nwhich is the number of times of extracting the backoff counter candidatevalue.

As such, according to the exemplary embodiment of the present invention,when the terminal transmits the data by using the wideband channel, theadditional backoff counter is derived to be used in the backoffprocedure to maintain the fairness of the data transmission opportunitywith the terminals of another BSS.

FIG. 26 illustrates yet another exemplary embodiment of the datatransmitting method using the wideband channel. According to theexemplary embodiment of FIG. 26, when the terminal transmits the data byusing the wideband channel, the bandwidth extension from the primarychannel may be gradually performed.

As described in the aforementioned exemplary embodiment, the terminalwhich intends to transmit the data performs the backoff procedure forthe primary channel CH1 and when the backoff counter is expired, theterminal transmits the data by using the primary channel CH1. However,unlike the previous exemplary embodiments, the terminal performs the CCAfor the secondary channel for the xIFS time after the backoff counter isexpired to determine whether the corresponding channel is usable. Inthis case, the xIFS may be set to PIFS as described in the previousexemplary embodiments regarding the bandwidth extension or alternativelyset to another value. When the corresponding secondary channel is idlefor the set xIFS time, the terminal transmits the data by using thecorresponding secondary channel together with the primary channel CH1.The terminal repeats the same process with respect to an additionalsecondary channel for the xIFS time after starting the occupation of thesecondary channel.

The terminal may extend the bandwidth by the unit of one channel whileperforming the bandwidth extension, and alternatively extend thebandwidth by the unit of a predetermined number of channels. Further, anorder to add the secondary channel for the bandwidth extension may bedetermined based on a merging or association order with the primarychannel according to the wideband allocation rule, but the presentinvention is not limited thereto. As such, according to the exemplaryembodiment of FIG. 26, when the terminal performs channel extension forusing the wideband channel, the terminal may gradually extend thechannel with a time difference of the predetermined xIFS to grant anopportunity in which other communication terminals may start thecommunication.

Although the present invention is described by using the wireless LANcommunication as an example, the present invention is not limitedthereto and the present invention may be similarly applied even to othercommunication systems such as cellular communication, and the like.Further, the method, the apparatus, and the system of the presentinvention are described in association with the specific embodiments,but some or all of the components and operations of the presentinvention may be implemented by using a computer system having universalhardware architecture.

The detailed described embodiments of the present invention may beimplemented by various means. For example, the embodiments of thepresent invention may be implemented by a hardware, a firmware, asoftware, or a combination thereof.

In case of the hardware implementation, the method according to theembodiments of the present invention may be implemented by one or moreof Application Specific Integrated Circuits (ASICSs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, micro-controllers, micro-processors,and the like.

In case of the firmware implementation or the software implementation,the method according to the embodiments of the present invention may beimplemented by a module, a procedure, a function, or the like whichperforms the operations described above. Software codes may be stored ina memory and operated by a processor. The processor may be equipped withthe memory internally or externally and the memory may exchange datawith the processor by various publicly known means.

The description of the present invention is used for exemplification andthose skilled in the art will be able to understand that the presentinvention can be easily modified to other detailed forms withoutchanging the technical idea or an essential feature thereof. Thus, it isto be appreciated that the embodiments described above are intended tobe illustrative in every sense, and not restrictive. For example, eachcomponent described as a single type may be implemented to bedistributed and similarly, components described to be distributed mayalso be implemented in an associated form.

The scope of the present invention is represented by the claims to bedescribed below rather than the detailed description, and it is to beinterpreted that the meaning and scope of the claims and all the changesor modified forms derived from the equivalents thereof come within thescope of the present invention.

MODE FOR INVENTION

As above, related features have been described in the best mode.

INDUSTRIAL APPLICABILITY

Various exemplary embodiments of the present invention have beendescribed with reference to an IEEE 802.11 system, but the presentinvention is not limited thereto and the present invention can beapplied to various types of mobile communication apparatus, mobilecommunication system, and the like.

1. A wireless communication method of a terminal, the method comprising:obtaining first primary channel information of a basic service set (BSS)with which the terminal is associated; performing clear channelassessment (CCA) for one or more secondary channels of the BSS; andsetting a second primary channel among one or more secondary channelsdetermined to be idle based on a result of the CCA.
 2. The wirelesscommunication method of claim 1, wherein the second primary channel israndomly set among the one or more idle secondary channels.
 3. Thewireless communication method of claim 1, wherein a secondary channel,among the one or more idle secondary channels, which forms a channelhaving the largest bandwidth in association with another idle secondarychannel(s) is set as the second primary channel.
 4. The wirelesscommunication method of claim 1, wherein the second primary channel isset based on a frequency interval between each of the idle secondarychannels and the first primary channel.
 5. The wireless communicationmethod of claim 1, wherein a secondary channel, among the one or moreidle secondary channels, having the highest order of association withthe first primary channel when applying a bandwidth extension forwideband data transmission is set as the second primary channel.
 6. Thewireless communication method of claim 1, wherein the first primarychannel is set common to each terminal in the BSS and the second primarychannel is set independently for each terminal in the BSS.
 7. A wirelesscommunication method of a terminal, the method comprising: obtainingfirst primary channel information of a basic service set (BSS) withwhich the terminal is associated; obtaining second primary channelinformation set for the terminal, the second primary channel being setamong at least one of the secondary channels of the BSS; performing abackoff procedure for each of the first primary channel and the secondprimary channel; and transmitting data by using at least one channelbetween the first primary channel and the second primary channel inwhich a backoff counter of the backoff procedure is expired.
 8. Thewireless communication method of claim 7, wherein a second backoffcounter for the backoff procedure of the second primary channel is setequal to a first backoff counter for the backoff procedure of the firstprimary channel.
 9. The wireless communication method of claim 8,wherein when the backoff procedure of the first primary channel issuspended, the backoff procedure of the second primary channel issimultaneously suspended during the suspension period of the backoffprocedure of the first primary channel, and when the second primarychannel is continuously maintained to be idle while the backoffprocedure of the second primary channel is performed, the data istransmitted by using the second primary channel.
 10. The wirelesscommunication method of claim 7, wherein the first backoff counter forthe backoff procedure of the first primary channel and the secondbackoff counter for the backoff procedure of the second primary channelare set independently from each other.
 11. The wireless communicationmethod of claim 10, wherein when the second backoff counter is expiredearlier than the first backoff counter, the terminal defers the datatransmission using the second primary channel until the first backoffcounter is expired, and when the first backoff counter is expired, thedata is transmitted by using both the first primary channel and thesecond primary channel.
 12. The wireless communication method of claim7, wherein the backoff procedure of the first primary channel and thebackoff procedure of the second primary channel are performed by using acommon backoff counter, and the common backoff counter is suspended whenboth the first primary channel and the second primary channel are busy.13. The wireless communication method of claim 12, wherein when thecommon backoff counter is expired, the data is transmitted by using atleast one channel between the first primary channel and the secondprimary channel which is idle.
 14. The wireless communication method ofclaim 7, further comprising: performing clear channel assessment (CCA)for secondary channels of the BSS for a predetermined time before thebackoff counter of the backoff procedure of the second primary channelis expired, wherein when at least one idle secondary channel which canbe associated with the secondary primary channel is present as a resultof performing the CCA, the data is transmitted through a widebandchannel in which the second primary channel and the idle secondarychannel are associated with each other.
 15. A wireless communicationterminal comprising: a transceiver configured to transmit and receive aradio signal; and a processor configured to control an operation of theterminal, wherein the processor further configured to: obtain firstprimary channel information of a basic service set (BSS) with which theterminal is associated, perform clear channel assessment (CCA) for oneor more secondary channels of the BSS, and set a second primary channelamong one or more secondary channels determined to be idle based on aresult of the CCA.